1. Field of the Invention
The present invention relates to a secondary battery, and more particularly, to a secondary battery having an improved structure capable of easily injecting an electrolytic solution into the battery.
2 Description of the Related Art
Unlike primary batteries incapable of charging, secondary batteries that are capable of charging and discharging, are widely used in advanced electronic devices such as mobile phones, notebook type computers, camcorders and the like. In particular, lithium secondary batteries are being rapidly developed because they have a service life 3 times longer than nickel-cadmium batteries or nickel metal hydride batteries which operate at 3.6 V and are widely used as the power source for electronic devices, and have high-energy density per unit weight.
Such lithium secondary batteries use lithium oxide as a positive electrode active material and a carbon material as a negative electrode active material. According to the kind of electrolyte used, lithium secondary batteries are generally classified into lithium ion batteries using a liquid electrolyte and lithium polymer batteries using a solid electrolyte. Also, lithium secondary batteries are manufactured in various shapes, for example, cylindrical, rectangular or pouchy shape.
In the conventional cap plate, since there is no space to install a safety vent that ruptures due to an increase in internal pressure, there is a design limit in installing the safety vent in the cap plate.
Korean Patent Publication No. 2000-51285 discloses a secondary battery in which an electrode tab is welded to the opposite side of an electrolytic solution inlet in view of an electrode terminal pin, which is different from the above-described conventional secondary battery in that only one electrode tab is welded to a cap assembly and the other electrode tab is welded to the can. However, the disclosed secondary battery also has a limit in view of injection efficiency of an electrolytic solution because the electrolytic solution inlet is simply a perforated hole.